Biokepi API : Biokepi_pipeline_edsl.Pipeline_library.Input.Derive.ensure_one_flowcell

let ensure_one_flowcell_max files =
      let open Pvem_lwt_unix.Deferred_result in
      let flowcell_re = Re.compile (Re_posix.re {re|.*(\..+)?\.fastq\.gz|re}) in
      let flowcells =
        Pvem_lwt_unix.Deferred_list.while_sequential files
          ~f:(fun f -> match Re.Group.all (Re.exec flowcell_re f) with
            | [|_; flowcell|] -> return flowcell
            | _ -> fail (`Re_group_error
                           "Re.Group.all returned an unexpected number of groups."))
      in
      flowcells >>| List.dedup >>= fun flowcells ->
      if List.length flowcells > 1
      then fail (`Multiple_flowcells flowcells)
      else return files